Wow. That's a lot of background information you're asking for. Let's
see if I can give you the summary version. (You can get the details
from the docs.)
Slots are an attribute of the queue. Slots are also a complex and can
be set as a complex at the host level if you want to limit the number of
slots in use across all the queues on a host. Grid Engine does not
limit a job to the number of slots that it requests. It's up to the
user to be honest about how many slots are needed. For SMP jobs, you
can create an SMP PE that lets you requests multiple slots on a single
machine.
In the scheduler configuration (sched_conf(5)), you'll find the
load_formula attribute. If you want to fill up hosts, you can set it to
"-np_load_avg", and it will choose the host with the highest load
average for each job. Another solution is to set the
job_load_adjustments to "NONE". That will have the scheduler pick the
least loaded host and put as many jobs there as it can.
Daniel
jfprieur wrote:
> Hello,
>> I am a relative noob to the field of cluster computing, I have
> succesfully deployed a Rocks cluster (20 nodes, 8 cores and 8GB/node,
> default SGE install puts 8 slots/nodes which is fine) and jobs are
> running fine on a basic level.
>> I am now starting to tweak the queue configurations. This cluster only
> runs serial jobs for now but some of those eg. Gaussian, use SMP. The
> problem right now is that if the user sets 4 CPU's in his input file,
> when he qsubs a job, it still only takes 1 slot. I find a lot of
> references to setting the number of slots for parallel jobs, not so
> much for serial SMP jobs. I woke up this morning with one node having
> three 8 CPU jobs and an 18 load factor! ;)
>> Would it be as simple as adding -l slots=x to the users submission script?
>> I also see a lot of references about configuring the slots, ideally
> each slot on my machine would be 1 CPU and 1GB, where would this be
> configured, complexes?
>> Finally on the "Managing the scheduler" wiki page is states: "The
> scheduler looks for queue instances on the least-loaded hosts that
> meet the resource requirements of the first job in line." Is there any
> way to change this to the scheduler looks for the most-loaded host
> that meets the resources requirements. I would like nodes to fill up
> instead of everything being spread out, or is this a bad idea?
>> I have been reading through the documentation, it is fantastic but
> slightly overwhelming for a new user.
>> Thanks for your help,
> JF Prieur
> Research assistant for Dr. Guillaume Lamoureux,
> Department of Chemistry and Biochemistry,
> Concordia University, Montreal, QC, CANADA
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